The Id1 and Id3 genes and proteins are critical components of the angiogenic process and participate in a wide range of processes involved in cellular differentiation and proliferation. It is now known that Id proteins help regulate the release and recruitment of bone marrow derived and circulating endothelial precursor cells which help form the new blood vessels of tumors. Recently this same observation has been extended to neovascularization in the eye. For this reason, we propose that either preventing expression of Id1/Id3 genes or inhibiting the functions of the Id1 and Id3 proteins in the eye could be an effective way to prevent or treat ocular neovascularization. Inhibiting pathologic ocular angiogenesis is of critical importance because aberrant blood vessel formation leads to severe visual loss in age-related macular degeneration (ARMD), diabetic retinopathy (DR) and retinopathy of prematurity (ROP). We, and one other group, have successfully used an antisense molecule to Id1 to block angiogenesis in an animal model unrelated to the eye. Such an agent might be useful if administered intravitreally to the eye. In addition to its therapeutic potential, an antisense molecule would also find significant use as a tool for proof-of-concept experiments in animal models of human ocular disease. Thus, the over-all goal of the proposed research is to confirm that inhibition of Id1/Id3 gene expression is a useful approach for treating ocular diseases characterized by pathologic neovascularization. To accomplish these goals, we propose the following three specific aims: (1) Examine the role of Id1/Id3 in retinal angiogenesis by quantifying retinal neovascularization in a mouse model of ischemia-induced retinal neovascularization in mice deficient in Id1 and Id3 and by using an intravitreally delivered anti-DNA antisense oligonucleotide with known activity for blocking Idl expression and angiogenesis to duplicate the anti-angiogenic phenotype of the Id1/Id3 knockout mouse, (2) Use in vitro/in vivo Matrigel studies and the mouse hyperoxia model to test the activity of siRNA oligonucleotides and one additional antisense molecule, and (3) Optimize one or more DNA-based or siRNA acting oligonucleotides that demonstrate promising activity by evaluating various vehicles to improve the duration and effect of the agent and establishing a dose-response relationship for at least one of the active oligonucleotides. Accomplishing these aims will demonstrate the feasibility of using specific oligonucleotides to inhibit ocular angiogenesis by blocking Id1 expression. Phase II activities will expand the approach to include blocking Id3 expression, exploring the possibility of blocking both Id1 and Id3 expression and further optimization of the oligonucleotides and possibly oligonucleotide combinations in terms of activity, pharmacokinetics and bioavailability. In addition, candidate oligonucleotides will be evaluated in one or more additional animal models of human ocular disease such as the argon laser photocoagulation model in mice.